The present invention relates to a mechanism which provides a means of leveling an existing sidewalk or other concrete slab or grade which has had portions settle into the ground so as to become uneven over time. More specifically, to a mechanism by which a section of sunken concrete slab or sidewalk can be quickly and easily raised to its original position in a manner that does not damage it and allows for the injection of pressurized sand into the cavity created between the bottom of the uneven concrete slab and the settled ground.
Regardless of the care and skill used in the initial construction, sidewalks and other similar concrete slabs tend to become misaligned over time due to different rates of settlement of the earth. Uplift from freeze/thaw cycles or tree root lifting are also common causes of this slab misalignment. These problems cause cracks in the sidewalk to develop and can also cause step-like structures to occur between sections of the sidewalk. The end result of this condition is the creation of hazards to sidewalk users and liability for those who are responsible for their care, both of which are exacerbated by the fact that the resulting uneven surfaces are extremely difficult to clear of snow and ice during the winter months in the northern areas of the United States.
In the past, there was a number of ways these problems were solved. One of these was to completely remove the damaged section of concrete slab and then re-pour it. The problem with this method is that although it works very well, it is time consuming and expensive. The re-pour method also results in a checkerboard looking concrete slabs as the new portions are often a very different color from the older weathered sections. Another method that has been used with the step formation problem is to construct concrete or tar ramps from the lower section of the sidewalk to the upper. The problem with this method is that it still leaves uneven sidewalk surfaces that are hazardous and difficult to maintain.
A further method of leveling these settled concrete slabs was to remove the soil from the edges of the slab and inserting a mechanical or hydraulic jack underneath it. Once the jack is thus positioned, the settled concrete slab is raised back into its original position by the activation of the jack and processed sand is pumped into the created void. The problem with this method of slab repair is that it is very time consuming, expensive, and inaccurate. Additionally, the removal of the dirt, grass, and other ground related items leaves unsightly scars at the repair sight that can take many months to fully recover.
Another method that is often used to repair these settled sections of concrete slabs is known as mud jacking. In this repair method, a hole is drilled through the uneven slab and wet mud is pumped at relatively high pressure under the slab until the slab becomes level. One problem with this method of slab repair is that it requires that the user drills and repairs a large number of unsightly holes in each individual un-cracked section of the concrete slab. An additional problem is that the use of wet mud often makes it difficult to effectively level a slab as the mud will settle over time while drying resulting in a finished repair containing the same deficiencies that prompted the need for it in the first place.
More recently, a number of patents have issued that attempt to deal with this problem in an effective and cost efficient manner. In U.S. Pat. No. 4,962,913, Stewart, Oct. 16, 1990, a method of lifting and repairing such damaged sidewalks is provided. The problem with this device is that by nature of its construction, a heavy frame supported four wheels, it is large and cumbersome in operation. Further, this device requires the even lifting of a given slab in only small sections at a time, as one portion of the device rests on an unlifted portion of the sidewalk. In U.S. Pat. No. 4,982,930, Stewart, Jan. 8, 1991, the same inventor attempted to resolve the short comings of his prior art by lightening the frame and removing the wheels. However, the resulting apparatus is still large and cumbersome in its operation. Also, as can be seen by both these solutions, the lifting methods provided block the sidewalk while the repair is in progress. Finally, the prior art does not provide a means by which the large concrete slabs associated with freeways and airport runways can be easily lifted to effectuate the necessary repairs.
Therefore, from the foregoing discussion it can be clearly seen that it would be desirable to provide a means of leveling existing concrete slabs in an inexpensive and effective manner. Additionally, that such a concrete slab leveling device be capable of lifting any size of settled slab from a small piece of sidewalk to a huge section of concrete runway, and finally, it would be desirable that such a concrete slab leveler be capable of providing a long lasting repair that is itself not subject to the problems associated with settling. Furthermore, the present invention also offers other advantages over the prior art and solves problems associated therein.